Electron valve



Dec. 31, 1940. N A m I 2,227,046

ELECTRON VALVE Original Filed Jan. 31, 1933 Patented Dec. 31, 1940ELECTRON VALVE Ernst Waldschmidt, Berlin, Germany, assignor, by mesneassignments, to Loewe Radio, Inc., a corporation of New York Originalapplication January 31, 1933, Serial No.

654,378. Divided and this application November 20, 1935, Serial No.50,760.

February 2, 1932 2 Claims.

sulating member surrounding the heating element, an equipotential layerprovided onthe insulating member, and an emissive coating provided onthe equipotential layer, which coating may consist, for example, of analkaline earth exide or of oxidized tungsten, and be activated or madecapable of emission by the application, by atomization, of barium.

It has been found that cathodes of this nature are frequentlyaccompanied by acoustical disturbances, such as humming noises and thelike. Thorough investigations have shown these disturbances to becreated by the fact that in the course of production of the cathodesabove referred to the metallic vapor is deposited not only on the highlyemissive layer to be activated, but on the insulating member as well. Byreason of this deposit located outside of the actual highly emissivelayer shunts are produced, and there is caused a detrimental subsidiaryemission. The present application is a divisional application ofapplication Ser. No. 654,378 filed January 31, 1933, describing the samematter.

The subject matter of the invention is a cathode, in which thesedisturbances are avoided. According to the invention, the cathode isformed in such fashion that the coating of atomized activating materialformed outside of the actual emissive area is unable to act indisturbing fashlOIl.

It has been found that these sources of error may be avoided, if theequipotential layer is so formed and arranged, that the coating producedat the ends of the insulating tube are unable to cause shunts.

According to the invention the equipotential surface consists of twotubes fitted one within the other, one of the tubes being longer thanthe other.

An embodiment of the invention is illustrated in the drawing.

In the drawing the equipotential surface consists of two tubes fittedone within the other.

' The outer tube 2 is longer than the inner tube 6.

l is the highly emissive coating, 3 the insulating tube and 4 thefilaments with the current leads 5, 9 and Ill two electrodes, e. g. gridand anode. Owing to this particular form of the equipotential layer ametallic coating formed on the ends of the insulating tube is unable tocause shunts, because no emissive layer will be deposited on the part Iof the insulating tube between the ends of the tubes 2 and 6.

I claim:

In Germany 1. An electron valve containing an indirectly.

heated cathode, control electrode and output electrode, said cathodecomprising an elongated heater element, an insulating tube membercompletely surrounding the heater element, a first metallicequipotential surface surrounding the insulating tube member having alength materially less than the length of the insulating tube member,the ends of said first metallic surface being spaced substantiallyequidistant from the ends of the insulating tube member, a secondmetallic equipotential surface surrounding the first metallicequipotential surface having a length greater than the length of said,first equipotential surface and less than the length of the insulatingtube member, the ends of said second metallic equipotential surfacebeing spaced substantially equidistant from the ends of the insulatintube member and from the ends of the first equipotential surface, and alayer of electron emissive material deposited on the outer surface ofsaid second equipotential surface whereby a portion of said insulatingtube member extending beyond the ends of said first equipotentialsurface will be shielded by said second equipotential surface.

2. An electron valve containing an indirectly heated cathode, controlelectrode and output electrode, said cathode comprising an elongatedheater element, an insulating tube member completely surrounding theheater element, a first metallic equipotential surface surrounding theinsulating tube member having a length materially less than the lengthof the insulating tube member, the ends of said first metallicsurfacebeing spaced substantially equidistant from the ends of the insulatingtube member, a sec-" ach other, and a layer of electron emissive ma- Iterial deposited on the outer surface of said second equipotentialsurface whereby a portion of said insulating tube member extendingbeyond the ends of said first equipotential surface will be shielded bysaid second equipotential surface.

ERNST WAIDSCHMIDT.

